An MPEG2 system (ISO/IEC 13818-1 GENERIC CODING OF MOVING PICTURES AND ASSOCIATED AUDIO: SYSTEMS Recommendation H.222.0) is used in a digital broadcast (digital satellite broadcast, digital terrestrial broadcast, and digital CATV (Cable Television)) in Japan. Such a system has been formed on the basis of the standard of ARIB (Association of Radio Industrial and Businesses).
The MPEG2 system specifies a system for multiplexing each of individual streams such as encoded video data, audio data, additional data, and the like and reproducing while synchronizing them. There are two kinds of systems such as MPEG2-PS (Program Stream) and MPEG2-TS (Transport Stream).
Since the MPEG2-PS has been made by presuming an application to transmission and storage of data in an environment where no errors occur and redundancy can be reduced, it is used in a digital storage media such as a DVD (Digital Versatile Disc) or the like using a powerful error correction code.
Since the MPEG2-TS has been made by presuming an application to an environment such as broadcast, communication network, or the like where a transmission error of data occurs and a plurality of programs can be constructed in one stream, it is used in a digital broadcast or the like.
In the MPEG2-TS, a plurality of TS (Transport Stream) packets of a fixed length of 188 bytes are collected and the transport stream is formed. The length of TS packet of 188 bytes has been determined in consideration of matching performance with an ATM (Asynchronous Transfer Mode) cell length.
The TS packet is constructed by a packet header of a fixed length of 4 bytes and an adaptation field and a payload each having a variable length. A PID (packet identifier) and various flags are defined in the packet header. A kind of TS packet is identified by the PID.
A PES (Packetized Elementary Stream) packet in which the individual streams of video, audio, and the like have been enclosed is divided into a plurality of TS packets having the same PID number and transmitted. For example, the MPEG2 system is used for encoding the video data. For example, in a BS (Broadcast Satellite) digital broadcast, an MPEG2-AAC (MPEG2 Advanced Audio Coding) system is used for encoding the audio data.
A PES packet in which data such as subtitles or the like is enclosed is also divided into a plurality of TS packets and transmitted in a manner similar to the packet of the video data or audio data.
Further, a packet of information described by a table in a section format such as PSI (Program Specific Information) or SI (Service Information) is included in the transport stream. The PSI is information which is necessary in a system which selectively receives a desired broadcast channel. A PAT (Program Association Table), a PMT (Program Map Table), an NIT (Network Information Table), a CAT (Condition Access Table), and the like can be given as PSI.
The PID or the like of the PMT corresponding to the program number is described in the PAT. A video image, an audio sound, and additional data included in the corresponding program and a PID of a PCR are described in the PMT. Detailed information regarding the whole broadcasting system is described in the NIT. For example, information of all programs included in a network and information showing at which carrier frequency a target program is transmitted are described. Information regarding identification of a limited receiving system and the individual information such as contract information and the like is described in the CAT. The SI indicates a section which is used for services of a broadcast industrial company. There are an EIT (Event Information Table) and an SDT (Service Description Table) as SI. Detailed information, a broadcasting time, and the like of the program are described in the EIT. The EIT is used for an EPG (Electronic Program Guide) and a recording reservation.
As a digital broadcast of such an MPEG2 system, a digital CS (Communication Satellite) broadcast and a digital BS (Broadcast Satellite) broadcast have already been started in Japan. In the digital BS broadcast, besides an ordinary SDTV (Standard Definition Television), a broadcast of an HDTV (High Definition Television) is being performed. Execution of a digital terrestrial broadcast is also being examined.
To protect a copyright of a motion image which is transmitted by such a digital broadcast, a digital copy control descriptor (digital_copy_control_descriptor) has been defined in ARIB STD-B10 (refer to FIG. 1). The digital copy control descriptor (digital_copy_control_descriptor) is inserted into the PMT, EIT, and SDT. In the case of copying the motion image which is transmitted by the digital broadcast, copying is restricted by such a descriptor.
Two bits of digital_recording_control_data in the digital copy control descriptor (digital_copy_control_descriptor) are used for copy control. When those two bits are equal to “00”, it indicates “Copy Freely” (the copy can be freely performed), “11” indicates “Copy Never” (the copying is inhibited), and “10” indicates “Copy One Generation” (the copy of only one generation is permitted). That is, those two bits are used to make the copy control of a CGMS (Copy Generation Management System). The copy control by the CGMS has been disclosed in, for example, Patent Document (JP-A-2000-123480).
Further, a content availability descriptor (content_availability_descriptor) is defined for the motion image (refer to FIG. 2). In the content availability descriptor (content_availability_descriptor), resolution can be restricted in the case of outputting the stored image or a recording time when a copy-inhibited image is temporarily recorded into a video recording and reproducing apparatus can be restricted.
In the content availability descriptor (content_availability_descriptor), image_constrain_token is used to restrict the resolution in the case of outputting the stored image in an analog manner. retention_mode shows whether to restrict a recording time when the copy-inhibited image is temporarily recorded or not. retention_state shows a recording restricting time when the copy-inhibited image is temporarily recorded. When retention_mode is equal to “0”, the image can be temporarily stored only for the time shown by retention_state. encryption_mode shows whether to encrypt the data of contents and output it from a high-speed digital terminal or not.
In recent years, the video recording and reproducing apparatus using an HDD (Hard Disk Drive) has been proposed. The video recording and reproducing apparatus using the HDD has a function to store the motion image which is being received, and when the user has a visitor or the like, freeze a receiving display screen and when the visitor has left, follow-up reproduce the motion image recorded in the HDD from the frozen position. retention_state of the content availability descriptor (content_availability_descriptor) is effective, particularly, in the case where copy restriction of copy-inhibited contents is made in the video recording and reproducing apparatus having such a function.
As mentioned above, the protection of the copyright of the motion image is realized by inserting the digital copy control descriptor (digital_copy_control_descriptor) or the content availability descriptor (content_availability_descriptor) into the PMT.
However, a system which transmits copyright information of a still image in the broadcast does not exist. Therefore, a violation act of a copyright law is still performed. The still image has rights such as copyright, right of portrait, and the like and it is demanded to establish a system which transmits and manages the copyright information of the still image contents.
As a still image with a possibility of being illegally used, there are a still image obtained by freezing the motion image and extracting a part of the motion image and a still image which is transmitted by a data broadcast service.
That is, the motion image is fundamentally a continuation of still images. In the digital broadcast, there are the following video formats: 1080i (1920×1080, interlaced scan); 480p (720×480, progressive scan); 480i (720×480, interlaced scan); 720p (1280×720, progressive scan); (1080p 1920×1080, progressive scan); and the like. The still image is obtained by freeze-reproducing the motion image. In the case of a signal of the video format such as 1080i, 1080p, or 720p, the still image obtained by freezing the motion image also has a fairly high picture quality.
The data broadcast service can be executed in the digital broadcast. In the data broadcast service, multimedia contents such as motion image, still image, characters, figure, subtitles, and the like can be handled. By using a browser, those multimedia contents can be linked and viewed. The still image encoded by a JPEG (Joint Photographic Experts Group) system or the like is derived from the data broadcast service.
As mentioned above, also with respect to the still image extracted as a part of the motion image or the still image which is transmitted by the data broadcast service, it is necessary to protect the copyright and prevent the still image from being illegally copied, illegally printed, or illegally attached to a homepage or the like.